The x-ray densitometer was installed at the Boston VA Outpatient Clinic in April, 1998 and the study technician was certified for bone density measurements during the three-day training session that followed. A precision study was conducted in the following month. In vivo reproducibility was determined by performing 5 repeat scans of each of the three sites on 5 volunteers ranging in age from 21 to 50 years. Subjects were repositioned between each scan. The coefficient of variation (CV) of femoral neck BMD in our laboratory is 0.92%; for whole body BMD, 0.72%; and for distal radius BMD, 1.04%. An aluminum spine phantom with known density (1.254 gm/cm2) is scanned every two weeks on the DPX-IQ. The mean ? standard deviation of 15 measurements is 1.250 ? 0.0058, coefficient of variation = 0.46%. There has been no detectable drift in phantom values during the study start-up phase.